This invention relates to jig saws, and more particularly to portable electric jig saws of the type sometimes referred to as saber saws or bayonet saws.
It has been recognized that significant improvements in the performance of jig saws of the present type can be achieved in many situations by providing a path of movement to the saw blade which is orbital in the vertical plane of the feed direction, rather than merely reciprocal along a straight line. However, under certain conditions, and for the sawing of certain materials, better results can still be obtained with straight line cutting. Consequently, jig saws have been developed which are capable of both types of operation, and which have manually adjustable means for varying the degree of orbital movement (i.e., the amount of displacement of the saw blade in the feed direction during each cycle thereof). In most of these known mechanisms blade displacement in the feed direction is accomplished by a guide roller which engages the trailing edge of the blade as it reciprocates vertically, means being provided to oscillate the guide roller back and forth in the feed direction on each cycle of the blade.
Most known mechanisms for achieving adjustable orbital blade movements have a significant drawback in that they reduce the degree of orbital blade movement merely by mechanically interrupting movement of the guide roller. This results in substantial lost motion in the orbital drive train, and attendant slapping of the parts, when the mechanism is set for less than full orbital action. The abrupt motion is noisy, causes the saw teeth to impact the workpiece and can result in tooth damage in high loading conditions, and increases wear and vibration.
Another disadvantage of these "lost motion" mechanisms is that the path of the saw blade is not a true orbital path when set for less than full orbital action. As a consequence, not all of the saw teeth are used in each cycle, reducing sawing efficiency.
It is a primary object of the present invention to provide an improved orbital jig saw which may be easily manually adjusted from full orbital action to a straight line action and which overcomes the aforementioned disadvantages of known mechanisms. The mechanism of the present invention provides infinite adjustment of the orbital path while at all times maintaining a smooth uninterrupted true orbital sawing action with no lost motion, thereby reducing tooth impact, wear, noise, vibration and the like, while maximizing the use of all saw teeth to improve sawing efficiency.
Further objects of the invention reside in the provision of a portable orbital jig saw ideally suited for heavy-duty professional use, yet which is relatively compact in size and relatively light in weight.
These and other objects, features and advantages of the present invention will become apparent from the subsequent description and the appended claims, taken in conjunction with the accompanying drawings.